1. Field
The present disclosure relates to wireless communication, and more particularly, to a method and an apparatus for operating a buffer state report when a user equipment performs a device-to-device communication using a resource allocated by a base station in a wireless communication system supporting device-to-device communication.
2. Discussion of the Background
Device-to-device (D2D) communication relates to a communication method having been available since the era of an analog two-way radio and has been used over the very long history. However, D2D communication in a wireless communication system is distinguished from existing D2D communication.
The D2D communication in the wireless communication system indicates communication that uses a transmission and reception technology, for example, a physical channel, of the wireless communication system in a frequency band of the wireless communication system or a band excluding the frequency band, and in this instance, enables user data to be directly transmitted and received between devices, for example, user equipments (UEs) without using an infrastructure, for example, an evolved-NodeB (eNB). That is, two UEs function as a source and a destination of data, respectively, and perform communication. Such a method enables wireless communication to be available in an area outside a limited wireless communication infrastructure and also decreases network load of the wireless communication system. For D2D communication in a wireless communication system, a base station may schedule resources needed for in-coverage UEs to transmit data via D2D communication. To this end, a UE may notify the base station through a buffer state report (BSR) of how much data is in a UE buffer to be transmitted via D2D communication.
In an exceptional case, a UE may transmit D2D data through a resource that the UE autonomously selects, instead of being allocated by the base station a resource necessary to transmit data via D2D communication. For this case, when an already triggered BSR is present in the UE, it needs to be determined how the UE handles the already triggered BSR before, and there is also a need for a detailed BSR operation and definition of the BSR.